Mechanical interlock



Feb. 15, 1938.

G. o. wlfLMs 2,108,634

MECHAN I CAL INTERLOCK Filed March 13, 1936 2 Sheets-Sheet l CWM..

Feb. 15, 1938. G. o. wlLMS 2,108,634

MECHANICAL INTERLOCK Filed March 15, 1956 2 Sheets-Sheet 2 Patented Feb. l5, 1938 PATENT ol-Fic MECHANICAL INT1-:BLOCK Gustav 0. Wilma, Milwaukee, Wis., assigner to Allen-Bradley Company,

Milwaukee, Wis., a

corporation of Wisconsin Application March 13, 1936, Serial No. 68,620

This invention relates to mechanical interlocks and refers particularly to mechanism for interlocking two electric switches so as to prevent closure of one switch while the other switch is 5 closed.

Mechanical interlocks heretofore in use for this purpose consisted merely of a walking beam acting directly in conjunction with moving parts of theswitches. This type of interlock functions l satisfactorily with the clapper type of switch of -the different sizes. but with the solenoid type, such as shown in Letters Patent No. 1,981,534, issued to Gustav O. Wilms and Albert J. Dawe, November 20th, 1934, the distance of travel of l the switch armature especially in the smaller switches is insumcient to properly operate this type of interlock. With the walking beam type of interlock, nity per cent of the total travel of the actuating armature is required to eilect the desired lock-ou of the switch being opened or held against closure, and if the available motion is small, the play between the moving parts may one of the switches is multiplied in its eil'ect upon 'the otheriswitch so that a small motion of the closing switch is sumcient to positively prevent closure of the other switch.

This object of the invention is achieved through use of connected Acams so associated with parts movable with the switches that closure of one of the switches results in a multiplied opening movement oi' the other switch or of the means used to obstruct closure ofthe -switch in the event it is open.

40 Another object of this invention is to provide an interlock of the character described which is exceptionally simple in design and rugged in construction.

Another object of this invention is to provide a mechanical interlock of the character described which is so constructed that its application to two associated switches entails no alteration in their design or construction.

Another object of this invention is to provide a mechanical interlock which is readily adjustable to accommodate variations in the distances between the switches with which it operates. l

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of `parts substantially as hereinafter described and more particularly dened by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as 5 come within the scope of the claims.

The accompanying drawings illustrate two complete examples of the physical embodiment of the invention constructed according to the best modes so far devised for the practical applica- 1u tion of the principles thereof, and in which:

Figure 1 is a front view of two electric switches mounted side by side and illustrating the interlock of this invention applied thereto;

Figure 2 is a perspective view of the interlock lo per se; and

Figures 3 and 4 are plan views of a modified embodiment of the invention showing the same in its two operative positions.

Referring now particularly to the accompany- `20 ing drawings in which like numerals indicate like parts throughout the several views, the numeral 5 designates a base or panel upon which two switches 6 and 1 are mounted in side by side relation. The switches illustrated are oi' the 25 type shown in the aforesaid letters Patent No. 1,981,534 issued to Gustav O. Wilms and Albert J. Dawe, November 20th, 1934, and reference may be had thereto for details oi' construction, which, however, i'orm no part of this invention. 30

These switches are of the vertical type in which an armature 8 moves vertically in response to the energization oi an electromagnet 9 to engage the cooperating contacts located within an arc hood structure ill. As will be evident, the arma- 35 tures 8 have a defined range of vertical motion and when the switches are mounted, as shown, in side by side relation, the motion of the armatures is parallel.

The mechanical interlock shown in Figures 1 40 and 2 and indicated generally by the numeral II coacts with the movable armatures and holds one down in its switch open position as long as the other armature is in its raised switch closing position. 45

In this embodiment of the invention, the interlock consists of two cams I2 and Il'associated with the switches 6 and 1, respectively. The cams are in the shape of bell crank levers and respectively pivotally mounted as at i4 and l5 50 Afrom the base or panel 5 in such positions that their apexes which carry studs I6 and il, respectively, face each other and their outer arms I8 and I9, respectively, point outwardly toward the lines of motion of the armatures l. r

The mounting of the switches is such that the armatures move in paths spaced from the panel .5 thus allowing space between the armatures and the panel to accommodate the bell crank levers, and the location of the pivotal mountings I4 and I5 for the bell crank levers is so related to the lines of motion oi the armatures that the outer arms I8 and I9 of the levers are engageable with studs 2U and 2| fixed to the armatures of the switches 6 and 1, respectively. i

Through this engagement between the outer arms of the levers and the studs 20 and 2 I, movement of either amature from its switch open position to switch closed position will cause its lever to swing on its pivotal mounting toward the other lever. Also, when the levers are in their operative positions at which their outer ends are substantially horizontal, they will hold their respective armatures against upward motion necessary for closure ofA their respective switches as long as they are retained in such operative positions.

Joining the apexes of the bell crank levers is a link 22. This link has right and left hand threaded hook portions v23 and 24 entering a central correspondingly tapped nut member 25 provided with a lock nut 26. The link thus formsv substantially a turnbuckle. The looped ends of its hook portions are engaged over the studs I6 and I1 where they are held by cotter pins or any other suitable securing means.

The length of the link is so adjusted with respect to the distance between the pivotal mountings I4 and I5 that the motion of one lever produced by the closure of its associated switch carries the other lever to its operative position holding its associated armature against switch closing movement and vice versa. Also, if one of the switches is closed and the other switch is energized to eiect closure thereof,`the interlock will function to pull the closed switch open.

Where the twov interlocked switches are connected to a motor for reversing duty, the closure of both switches at the same time would result in a short circuit. On a quick reversal of the motor, it may so happen that the switch coil of the closed switch continues to be energized a brief time during the energization of the open switch. In this case, there is an overlapping of the switch coil circuit closures. condition, when the switch coil of the closed switch opens there is an almost instant closure of the open switch. The arc .occurring at the contacts of the closed switch which is now opening may continue until the contacts of the closing switch have touched, resulting in a short circuit. This undesirable condition may occur when the interlock oi the walkingbeam type is used on solenoid type switches.

I'he cam type interlock as disclosed herein, under the condition of the overlapping coil circuit closures, introduces suicient friction between the pins and their respective cams to slow down the motion of the closing switch to preclude any short circuit. In the embodiment of, the invention above described, the friction referred to results primarily from the sliding action between the outer arms Itand I9 and their respective pins 2B and 2l.

It is essential that the motion produced by the closure of the switch being closed be multiplied in its effect upon the other switch. To illustrate, when the pin .iti has moved two-fifths of its total upward travel, the pin 2t and consequently its armature have moved at least three- Under this i fths of its downward travel so as to positively preclude simultaneous closure of both switches. This desirable result is obtained through the proper location of the pivots I4 and I5 with respect to the line of motion of the pins 20 and 2|, and through proper disposition and shape of the arms I8 and I9 with respect to the swinging motion of the cams about their pivots I4 and I5.

While the embodiment o the invention illustrated in Figures 1 and 2 has proved very delsirable, especially where the associated switches are mounted side by side, the inventive concept also may be embodied in an interlock wherein the two cams are rigidly joined, as illustrated in Figures 3 and 4.

In this modiiication, the switches are mounted one abovethe other, as indicated in construction lines, so that their pins 20 and 2I move in substantially a common vertical plane. 'I'he cams 30 and 3l which coact with the pins 20 and 2|, respectively, are formed on the opposite ends of a lever 32 medially pivoted, as at 33.

The cam 30 is formed on the underside of a lateral projection and the cam 3| is provided by the lower curved edge. of the lever 32. To limit counter-clockwise rotation of the lever, a projection 34 is formed on the lower end of the lever to strike the pin 2I, as shown in Figure 4.

Particular attention is directed to the specific shape of the cams, which is such that the motion produced by the armature moving upwardly to close its respective switch is multiplied in its effect upon the armature of the closed switch.

It is also to be observed that the degree of sliding contact between the pins 20 and 2I and their respective cam surfaces 3i] and 3I is such as will produce a substantial component of friction for the purpose hereinbefore set forth.

From the foregoing description taken in connection with the accompanying drawings, it will be readily apparent to those skilled in the art to which this invention appertains, that this invention provides a compact and extremely simple mechanism for mechanically interlocking two switches or any other units in which concomitant motion `is to be avoided, and that notwithstanding the small travel available, positive lock-out is obtained,

What I claim as myinvention is:

1. In combination with two side by side movable members, a mechanical interlock for locking said members against concomitant motion in the same direction,l said interlock comprising'a pair of bell crank levers, fixed pivots mounting the levers at the outer ends of corresponding arms with the apexes of the levers facing each other andthe free arms thereof arranged to engage the movable members, anda link connecting the apexes of said levers, said linkbeing of such length with respect to the distance between the xed pivots that when one lever is in a position permitting movement of its associated movable member in said direction the other lever is held in a position positively preventing movement of its associated movable member.

2. A mechanical interlock for two electrical switches to prevent concomitant closure of both switches, said switches having members movable upon opening and closing thereof, a pair of bell crank levers, means pivotally mounting said levers at the outer ends of corresponding arms with the apexes of the levers :facing each other and the other arms thereof extending outwardly for engagement with said movable members, and

Aalong defined paths in l member 9,108,834 a link joining the apexes of the levers, said link being of such length that when one o1' the levers is in its Aposition permitting movement oi' its associated member incident to lclosure of its switch the otherlever is in a position engaged with its associated movable member to positively hold the same against movement necessary for closure of its switch.

3. A mechanical interlock toprevent concomitant closure of two electric switches, said switches including movable members which move consequence to closure of the switches, said inter lock comprising a hookshaped member for each switch, means movably mounting said hook-shaped members for operative engagement with the movable members o! the switches, said hook-shaped members having a part engageable over the movable members for holdingthe movable members against movement necessary forclosure oi their switches when said hook-shaped members are heldin one position, and a link connecting said hook-shaped members, said link being oi' such length that when one of said hook-shaped members is in its position permitting closure of its associated switch the other hook-shaped member is held in its position preventing closure of the other switch.

4. In a mechanical interlock for useI in connection with two movable members whereby one o1' said members may be secured against movementv in one direction when the other member is in a predetermined position, said interlock comprising two pivoted members, one to coact with each of said movable members, said pivoted members each having an arm lying in the path of movement. of its movable member so as to be actuated thereby and swung toward the other pivoted member upon movement of the iirst mentioned movable member in one direction, said arms being so shaped as to hook over the movable members for holding the same against movement in said direction, and a link joining said pivoted members, said link being of such length that actuation of one pivoted member by its movable member as described moves the other pivoted member to its position at which the arm thereof hooks over and prevents movement oi itsassociated movable member.

5. A mechanical interlock for two electric switches whereby one switch may be locked against closure when the other is closed, said switches having movable members which move in correspondencel with the closure of their switches, said interlock comprising a pivoted @associated with each of said movable members with its pivoted mounting so located with respect to the path of movement of its associated movable member and so shaped that a part thereof at all times extends into the path of vmovement of the movable member, each pivoted member being engageable over its movable member to hold the same against movement necessary for switch closure, the disposition of said parts of the pivotal members in the paths of the movable members causing each pivotal member to be s img toward the other pivotal member upon movement of its associated movable member in correspondence to closure of its switch, and a link joining said pivoted members and `.of such length that movement of one piv' oted member caused byclosure of its associated switch moves .the other 'pivoted member to its operative position preventing closure of the other switch. 'fix' v 6. A mechanical interlock of the character described comprising two spaced hook members. means pivotally mounting said hook members in opposed relationship back to back with their hook portions movable upon swinging of said members between a position nearly horizontal in which they engage over parts to be restrained against movement and an unrestraining position inclined a substantial distance to the horizontal, and a link joining said hook members and holding them in such relative positions that when one hook member is in a position with its hook portion inclined upwardly from the horizontal the other hook member is in a position with its hook portion nearly horizontal.

7. A mechanical interlock of the character described comprising two bell crank levers, means pivotally mounting said levers from the ends oi corresponding arms in opposed relationship with their apexes facing each other and their other arms providing stops engageable with parts to be restrained against movement when said bell crank levers are in certain operative positions, and a link joining thev apexes of the bell crank levers and of such length with respect to the distance between their pivotal mountings as to hold one bell crank lever in its operative position while the other is in its opposite inoperative position.

.8. A mechanical interlock of the character described comprising two bell crank levers, means pivotally mounting said levers from the ends of corresponding arms and in opposed relationship with their apexes facing each other and their other arms providing hooks engageable over parts to be restrained against movement when said bell crank levers are in certain operative positions, a link joining the apexes of the bell crank levers and of suchvlength with respect to the distance between their pivotal `mountings as to hold one bell crank lever in its operative position while the other is in its opposite inoperative position, and means for adjusting the length of said link.

9. A mechanical interlock for two electrical switches which have straight line opening and closing motion with parts moving in the same direction with a translating motion, said interlock comprising two cams each mounted adjacent to one of said movable parts, said cams hav- -ing a shape and being so associated with said movable parts as to be moved laterally by the straight line translating motion of said parts in response to closure of their respectiveV switches, and a link joining said cams and holding the same in such relative positions that motion transmitted to one cam upon closure of its associated switch disposes the other cam in a position obstructing movement of its associated part to prevent closure of its respective switch.

10. In combination with a plurality of electrical switches, a mechanical interlock for positively opening a closed switch upon closure of an open switch, comprising a plurality of connected cams, one for each switch, a member associated with eachswitch and movable in a dened path upon opening and closing thereof, said members being slidable on the cams, and the cams being so shaped that motion of one of the members upon closure of its switch causes motion of the cams resulting' in a; multiplied opening motion of the member associated with the closed switch.

11. In combination with a plurality of electrical switches, a mechanical interlock for positively opening a closed switch upon closure of an open switch, comprising a plurality of connected cams,

one for each switch, a member associated with each switch and movable in a defined path upon opening and closing thereof, said members being slidable on the cams, and the cams being so shaped that motion of one of the members upon closure of its switch causes motion of the cams resulting in a multiplied opening motionof the member associated with the closed switch, and the distance of travel of the sliding Contact between the cams and their associated members being suicient to introduce a substantial component of friction acting against the actuating force to retard the closing of the open switch.

12. In combination with two associated electrical switches, a mechanical interlock for positively opening a closed switch upon closure of the other switch, said interlock comprising two connected cams, one for each switch, members movable with the switches upon opening and closing thereof and slidably connected with the cams so that closure of one switch moves the connected cams in a manner to pull the closed switch open, said cams being so shaped that the motion generated by the closing switch is multiplied in its eiect upon the switch being opened.

13. In combination with a plurality of electrical switches, a mechanical interlock for positively opening a closed switch upon closure of an open switch, comprising a plurality of connected cams, one for each switch, and a member movable with each switch upon opening and closing thereof,

said members being slidable on the cams to produce motion on the part of the cams angular to the direction of motion of said members upon closure of one switch, which angular motion is effective to open another switch, and the distance of travel of the sliding contact between the cams and their associated members being sufcient to introduce a substantial component of friction acting against the actuating force so as to retard closing of the open switch.

14. A mechanical interlock for two movable elements, each of which is movable in a straight line and in the same direction to a predetermined position, said interlock comprising two movable cams, one for each of said movable elements, said cams having a shape and being so associated with the movable elements as to be moved by the straight line motion of said elements to theirk said predetermined positions, and means joining said cams and holding the same in such relative positions that motion imparted to one cam by its associated movable element disposes the other cam in such relative position with respect to its associated movable element as to prevent movement thereof to its said predetermined position.

15. In combination with two associated electrical switches, each of which has a part moving in a definite path upon openingand closing of the switch, a vmechanical interlock for preventing closure of one switch when the other is closed, said interlock comprising two cams, one for each switch, said cams having a shape and being so associated with said movable parts of the switches as to be actuated by the motion of said parts in response to closure of their respective switches, and means joining said cams and holding them in such relative positions that actuation of one cam upon closure of its associated switch disposes the other cam in a position obstructing movement of its associated part necessary for closure of its switch so as to prevent such closure of its respec-t tive switch.

GUSTAV O. WILMS. 

